Developmental Biology is a core life sciences subject that explores how a single fertilized egg develops into a complex, multicellular organism. It integrates concepts from cell biology, genetics, molecular biology, and physiology to explain growth, differentiation, and pattern formation. This Developmental Biology exam past paper is designed to help students revise key topics, understand common examination trends, and practice structuring well-reasoned answers.
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Developmental Biology Exam Past Paper
Above is the past paper download link
Section A: Short Answer Questions
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Define developmental biology.
Developmental biology is the branch of biology that studies the processes by which organisms grow and develop, focusing on cell division, differentiation, morphogenesis, and gene regulation from fertilization to adulthood. -
What is fertilization?
Fertilization is the fusion of male and female gametes to form a diploid zygote, restoring chromosome number and initiating embryonic development. -
Distinguish between cleavage and gastrulation.
Cleavage involves rapid mitotic divisions of the zygote without growth, producing smaller cells called blastomeres. Gastrulation is the process by which these cells rearrange to form the three primary germ layers. -
Name the three germ layers and one derivative of each.
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Ectoderm: nervous system
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Mesoderm: muscles
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Endoderm: digestive tract lining
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What is apoptosis?
Apoptosis is programmed cell death that plays a critical role in shaping tissues and removing unnecessary or damaged cells during development.
Section B: Structured Questions
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Describe cleavage patterns in animals (10 marks).
Cleavage patterns vary among animals and depend largely on yolk content and distribution. In animals with little yolk, such as mammals, cleavage is holoblastic (complete). In contrast, birds and reptiles exhibit meroblastic (incomplete) cleavage due to large yolk masses. Radial cleavage, common in echinoderms, produces blastomeres aligned along the polar axis, while spiral cleavage, seen in annelids, results in obliquely oriented cells. These patterns influence later developmental processes and body plans. -
Explain the process of gastrulation (10 marks).
Gastrulation transforms the blastula into a gastrula with distinct germ layers. It involves cell movements such as invagination, involution, ingression, delamination, and epiboly. These movements establish the body axes and internal organization of the embryo. Gastrulation is crucial because it sets the foundation for organogenesis.
Section C: Essay Questions
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Discuss the role of gene regulation in development (20 marks).
Gene regulation is central to developmental biology, as all cells in an organism generally contain the same genetic material, yet differentiate into various cell types. Differential gene expression allows cells to acquire unique structures and functions. Regulatory genes, transcription factors, and signaling pathways work together to control when and where specific genes are activated. For example, homeotic (Hox) genes determine the identity of body segments along the anterior-posterior axis. Mutations in these genes can lead to dramatic developmental abnormalities. Epigenetic mechanisms such as DNA methylation and histone modification also influence gene expression without altering DNA sequence, ensuring stable cell identities during development. -
Describe organogenesis with reference to one organ system (20 marks).
Organogenesis is the phase of development during which organs form from the germ layers. Using the nervous system as an example, organogenesis begins with neurulation. The ectoderm thickens to form the neural plate, which folds into the neural tube. The neural tube gives rise to the brain and spinal cord, while neural crest cells migrate to form peripheral nerves and other structures. Proper signaling between tissues is essential; disruption can result in congenital defects such as spina bifida.
Section D: Applied Question
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Explain how developmental biology contributes to medicine (10 marks).
Developmental biology has significant medical applications, including understanding congenital disorders, improving regenerative medicine, and advancing stem cell therapy. Insights into normal development help identify the causes of birth defects, while stem cell research offers potential treatments for degenerative diseases and injuries.
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